Broad-temperature-range, efficient n-Type ionic thermoelectric cells enabled by pioneering hydrophobic crosslinked tough hydrogels

Ionic thermoelectric cells (i-TECs) can convert low-grade heat into electricity, but achieving stable performance across wide temperatures range with high thermopower and good mechanical durability remains difficult. This study presents a hydrophobic crosslinking strategy to fabricate fatigue-resistant hydrogel P(NAGA-co-VEIMBr) (PNVC) in one step. The hydrophobic macromolecular crosslinker imparts strong anti-swelling for importing thermoelectric ions. PNVC-based i-TECs show high thermoelectric performance, reversible elasticity, and excellent freeze resistance, allowing stable operation from −20 to 60 °C. The optimized PNVC i-TEC device achieves a thermopower of −10.86 mV K⁻¹ above 0 °C and −4.52 mV K⁻¹ subzero, along with a Young’s modulus of 0.21 MPa. A six-unit array can power an LED by harvesting body heat. PNVC i-TECs also enable self-powered multimodal sensing through small changes in resistance, voltage, or current, demonstrating its exceptional capability for self-powered sensing integrated applications. This hydrophobic crosslinking strategy offers a promising solution for facilely fabricate high performance ionic i-TE materials.